New research from last week 40/2012

Posted by Ari Jokimäki on October 8, 2012

Sun is the fireball in the sky that controlled Earth’s climate until mankind took the control. Sun still has some regional tricks, but in order to take back the control of global climate in near future, Sun would need to do some special tricks. Not Sun-related studies this week deal with climate scepticism, cloud height, methane emissions, ocean temperatures, Antarctic glaciers, 2011 sea level drop, ball lightning, surface specific humidity, model predictions, permafrost, past climate, European and East Asian summer temperatures, and some other things. There’s 15 studies + another 17 in other papers section, and I only include here a small fraction of all climate related papers. It was a rather busy week in climate science.

Solar forcing of Europe summer temperatures during last 1000 years

Abstract: “A simulation of the last millennium is compared to a recent spatio-temporal reconstruction of summer temperature over Europe. The focus is on the response to solar forcing over the pre-industrial era. Although the correlation between solar forcing and the reconstruction remains small, the spatial regression over solar forcing shows statistically significant regions. The meridional pattern of this regression is found to be similar in the model and in the reconstruction. This pattern exhibits a large warming over Northern and Mediterranean Europe and a lesser amplitude response over Central and Eastern Europe. The mechanisms explaining this pattern in the simulation are mainly related to evapotranspiration fluxes. It is shown that the evapotranspiration is larger in summer over Central and Eastern Europe when solar forcing increases, while it decreases over the Mediterranean area. The explanation for the evapotranspiration increase over Central and Eastern Europe is found in the increase of winter precipitation there, leading to a soil moisture increase in spring. As a consequence, the evapotranspiration is larger in summer, which leads to an increase in cloud cover over this region, reducing the surface shortwave flux there and leading to less warming. Over the Mediterranean area, the surface shortwave flux increases with solar forcing, the soil becomes dryer and the evapotranspiration is reduced in summer leading to a larger increase in temperature. This effect appears to be overestimated in the model as compared to the reconstruction. Finally, the warming of Northern Europe is related to the albedo feedback due to sea-ice cover retreat with increasing solar forcing.”

Solar effects on cloud cover are seen in some regions but are not visible at the global level

Abstract: “A consensus regarding the impact of solar variability on cloud cover is far from being reached. Moreover, the impact of cloud cover on climate is among the least understood of all climate components. This motivated us to analyze the persistence of solar signals in cloud cover for the time interval 1984–2009, covering two full solar cycles. A spatial and temporal investigation of the response of low, middle and high cloud data to cosmic ray induced ionization (CRII) and UV irradiance (UVI) is performed in terms of coherence analysis of the two signals. For some key geographical regions the response of clouds to UVI and CRII is persistent over the entire time interval indicating a real link. In other regions, however, the relation is not consistent, being intermittent or out of phase, suggesting that some correlations are spurious. The constant in phase or anti-phase relationship between clouds and solar proxies over some regions, especially for low clouds with UVI and CRII, middle clouds with UVI and high clouds with CRII, definitely requires more study. Our results show that solar signatures in cloud cover persist in some key climate-defining regions for the entire time period and supports the idea that, if existing, solar effects are not visible at the global level and any analysis of solar effects on cloud cover (and, consequently, on climate) should be done at the regional level.”

News coverage of climate scepticism is mostly limited to the USA and the UK

Abstract: “Previous academic research on climate scepticism has tended to focus more on the way it has been organized, its tactics and its impact on policy outputs than on its prevalence in the media. Most of the literature has centred on the USA, where scepticism first appeared in an organized and politically effective form. This letter contrasts the way climate scepticism in its different forms is manifested in the print media in the USA and five other countries (Brazil, China, France, India and the UK), in order to gain insight into how far the US experience of scepticism is replicated in other countries. It finds that news coverage of scepticism is mostly limited to the USA and the UK; that there is a strong correspondence between the political leaning of a newspaper and its willingness to quote or use uncontested sceptical voices in opinion pieces; and that the type of sceptics who question whether global temperatures are warming are almost exclusively found in the US and UK newspapers. Sceptics who challenge the need for robust action to combat climate change also have a much stronger presence in the media of the same two countries.”

Positive trend in cloud height globally

Abstract: “Measurements by the Multiangle Imaging SpectroRadiometer (MISR) instrument exhibit a decreasing trend in global mean effective cloud top height (2000–2011). Here we show that this trend is likely related to an artifact in the data present during the early years of the MISR mission that caused a systematic reduction in the number of retrievals of clouds at lower elevations relative to clouds at higher elevations. After the application of a post-hoc method for removing the bias associated with missing retrievals the MISR effective cloud height anomalies exhibit a positive trend over time.”

Global anthropogenic methane emissions 2005–2030

Abstract: “This paper presents estimates of current and future global anthropogenic methane emissions, their technical mitigation potential and associated costs for the period 2005 to 2030. The analysis uses the GAINS model framework to estimate emissions, mitigation potentials and costs for all major sources of anthropogenic methane for 83 countries/regions, which are aggregated to produce global estimates. Global emissions are estimated at 323 Mt methane in 2005, with an expected increase to 414 Mt methane in 2030. The technical mitigation potential is estimated at 195 Mt methane in 2030, whereof about 80 percent is found attainable at a marginal cost less than 20 Euro t−1 CO2eq when using a social planner cost perspective. With a private investor cost perspective, the corresponding fraction is only 30 percent. Major uncertainty sources in emission estimates are identified and discussed.”

Two independent observing networks show that global near surface ocean has warmed since 1900

Abstract: “We compare historical global temperature time series, based on bias-adjusted sea-surface temperatures with independent temperature time series, for the upper 20 meter layer of the ocean based on the latest update of an historical hydrographic profile data set. Despite the two underlying data sets being different in number of data points, instrumentation and applied adjustments, both of the time series are consistent in showing an overall warming since 1900. We also extend records of temperature change in the upper 400 m back to 1900. Noting that the geographic coverage is limited prior to 1950, the temperature change in the 0–400 m layer is characterized by two periods of temperature increase between 1900 and 1940–45 and between 1970 and 2003, separated by a period of little change.”

Accelerated thinning of Antarctic glaciers on the coast of the Amundsen Sea

Abstract: “Since 2002, the Envisat radar altimeter has measured the elevation of the Antarctic ice sheet with a repeat cycle of 35 days. This long and regular time series is processed using an along-track algorithm to depict in detail the spatial and temporal pattern of elevation change for the whole ice sheet. We use this dataset to examine the spatial and temporal pattern of Pine Island Glacier (PIG) thinning and compare it to the neighbouring glaciers. We also examine additional areas, especially in East Antarctica whose mass balance is poorly known. One advantage of the finer along-track spacing of measurements is that it reveals places of dynamic thinning in regions of rapid ice flow. We observe the acceleration of thinning on PIG. Over the entire basin, the volume loss increased from 7 km3 a-1 during 2002-06 to ∼48 km3 a-1 during 2006-10. We also observe accelerated thinning on the lower tens of kilometres of Thwaites Glacier, with a mean thinning of 0.18 m a-1 over its entire basin during our observation period. We confirm the dynamic thinning of Totten Glacier but we do not detect significantly accelerated thinning on any glacier elsewhere than on the coast of the Amundsen Sea.”

Sea level drop in 2011 was mainly caused by La Nina’s effect on water exchange between ocean and land

Abstract: “Global mean sea level (GMSL) dropped by 5 mm between the beginning of 2010 and mid 2011. This drop occurred despite the background rate of rise, 3 mm per year, which dominates most of the 18-year record observed by satellite altimeters. Using a combination of satellite and in situ data, we show that the decline in ocean mass, which explains the sea level drop, coincides with an equivalent increase in terrestrial water storage, primarily over Australia, northern South America, and Southeast Asia. This temporary shift of water from the ocean to land is closely related to the transition from El Niño conditions in 2009/10 to a strong 2010/11 La Niña, which affected precipitation patterns world-wide.”

Watching the birth of ball lightning

Abstract: “Many observations of ball lightning report a ball of light, about 10 cm in diameter, moving at about walking speed, lasting up to 20 s and frequently existing inside of houses and even aeroplanes. The present paper reports detailed observations of the initiation or birth of ball lightning. In two cases, navigation crew of aircraft saw ball lightning form at the windscreen inside the cockpit of their planes. In the first case, the ball lightning occurred during a thunderstorm, with much lightning activity outside of the plane. In the second case, large “horns” of electrical corona were seen outside of the plane at the surface of the radome, just prior to the formation of the ball lightning. A third case reports ball lightning formed inside of a house, during a thunderstorm, at a closed glass window. It is proposed, based on two-dimensional calculations of electron and ion transport, that ball lightning in these cases is driven and formed by atmospheric ions impinging and collecting on the insulating surface of the glass or Perspex windows. This surface charge can produce electric fields inside of the cockpit or room sufficient to sustain an electric discharge. Charges of opposite sign to those outside of the window accumulate on the inside surface of the glass, leaving a ball of net charge moving inside of the cockpit or room to produce a pulsed discharge on a microsecond time scale.”

Abstract: “We investigate whether the observed surface specific humidity (q) trends over the Mediterranean region in the period 1974–2003 are consistent with climate model (CMIP3, CMIP5) simulations of q in response to anthropogenic forcing (Greenhouse gas and sulphate aerosols). The natural (internal) variability is estimated using 6,000-year of pre-industrial control simulations. With the exception of winter, the increases in annual and seasonal q over this region are very unlikely (with less than 1%chance) due to natural (internal) variability or natural forcing alone. Using several climate models and ensemble means, we demonstrate that the large-scale component (spatial-mean trend) of the anthropogenic forcing is detectable (at 1% level) in the annual and seasonal trends of q (except winter). However, the smaller-scale component (spatial anomalies about the mean trend) of the anthropogenic signal is detectable only in warm seasons (spring and summer). We further show that the spread of projected trends based on the A1B scenario derived from 13 CMIP3 models encompasses the observed area-averaged trend in q. This may imply that the observed trends of surface humidity, which is an important factor in human thermal comfort, serves as an illustration of plausible future expected change in the region.”

Adjusting for model deficiencies in decadal predictions of global climate

Abstract: “A method for post-processing decadal predictions from global climate models that accounts for model deficiencies in representing climate trends is proposed and applied to decadal predictions of annual global mean temperature from the Canadian Centre for Climate Modelling and Analysis climate model. The method, which provides a time-dependent trend adjustment, reduces residual drifts that remain after applying the standard time-independent bias correction when the modelled and observed long-term trends differ. Initialized predictions and uninitialized simulations that share common specified external forcing are analyzed. Trend adjustment substantially reduces forecast errors in both cases and initialization further enhances skill, particularly for the first forecast year.”

How much permafrost will be lost during 21st century?

Abstract:“We analyze global climate model predictions of soil temperature (from the Coupled Model Intercomparison Project 5 (CMIP5) database) to assess the models’ representation of current-climate soil thermal dynamics, and their predictions of permafrost thaw during the 21st century. We compare the models’ predictions to observations of active layer thickness, air temperature, and soil temperature, and to theoretically-expected relationships between active layer thickness and air temperature annual mean and seasonal cycle amplitude. Models show a wide range of current permafrost areas, active layer statistics (cumulative distributions, correlations with mean annual air temperature and amplitude of seasonal air temperature cycle), and ability to accurately model the coupling between soil and air temperatures at high latitudes. Many of the between-model differences can be traced to differences in the coupling between either near-surface air and shallow soil temperatures, or between shallow and deeper (1m) soil temperatures, which in turn reflect differences in snow physics and soil hydrology. We compare the models to observational datasets to benchmark the permafrost-relevant physics of the models. The models show a wide range of predictions for permafrost loss: 2-66% for RCP2.6, 15-87% for RCP4.5, and 30-99% for RCP8.5. Normalizing the amount of permafrost loss by the amount of high-latitude warming in the RCP4.5 scenario, the models predict an absolute loss of 1.6 ± 0.7 million km2 permafrost °C−1 high-latitude warming, or a fractional loss of 6-29% °C−1.”

Climate reconstruction of past 14000 years from East Africa

Abstract: “New molecular proxies of temperature and hydrology are helping to constrain tropical climate change and elucidate possible forcing mechanisms during the Holocene. Here, we examine a ∼14,000 year record of climate variability from Lake Victoria, East Africa, the world’s second largest freshwater lake by surface area. We determined variations in local hydroclimate using compound specific δD of terrestrial leaf waxes, and compared these results to a new record of temperature utilizing the TEX86 paleotemperature proxy, based on aquatic Thaumarchaeotal membrane lipids. In order to assess the impact of changing climate on the terrestrial environment, we generated a record of compound specific δ13C from terrestrial leaf waxes, a proxy for ecosystem-level C3/C4 plant abundances, and compared the results to previously published pollen-inferred regional vegetation shifts. We observe a general coherence between temperature and rainfall, with a warm, wet interval peaking ∼10–9 ka and subsequent gradual cooling and drying over the remainder of the Holocene. These results, particularly those of rainfall, are in general agreement with other tropical African climate records, indicating a somewhat consistent view of climate over a wide region of tropical East Africa. The δ13C record from Lake Victoria leaf waxes does not appear to reflect changes in regional climate or vegetation. However, palynological analyses document an abrupt shift from a Poaceae (grasses)-dominated ecosystem during the cooler, arid late Pleistocene to a Moraceae-dominated (trees/shrubs) landscape during the warm, wet early Holocene. We theorize that these proxies are reflecting vegetation in different locations around Lake Victoria. Our results suggest a predominantly insolation-forced climate, with warm, wet conditions peaking at the maximum interhemispheric seasonal insolation contrast, likely intensifying monsoonal precipitation, while maximum aridity coincides with the rainy season insolation and the interhemispheric contrast gradient minima. We interpret a shift in conditions at the Younger Dryas to indicate a limited switch in insolation-dominated control on climate of the Lake Victoria region, to remote teleconnections with the coupled Atlantic and Pacific climate system.”

European summer temperature variability might increase in the future

Abstract: “Summer temperature variability has been projected to increase in Central Europe in response to anthropogenic greenhouse gas forcing. Based on an unprecedented set of global and regional climate models from the ENSEMBLES project, we assess the robustness of these projections on interannual to daily time scales. In comparison to previous analyses using PRUDENCE simulations, we find a more diverse climate change signal for interannual summer temperature variability and a clear dependence upon present-day model performance. Models that realistically represent present-day variability, tend to consistently project increasing interannual variability at the end of the 21st century. We demonstrate that the partitioning of latent and sensible heat fluxes controlled by soil moisture is crucial to understand the projected changes across the multi-model experiment. The projected increase in daily summer temperature variability is more robust and consistently simulated by all models. Likewise, all models consistently project reduced daily temperature variability in winter. Thus, it is a robust signal across the entire ensemble that in summer and south-central Europe hot extremes warm stronger than the mean, and in winter and northern Europe cold extremes warm stronger than mean temperatures.”

Why is there a summer cooling trend in East Asia?

Abstract: “Observations indicate a surface cooling trend during the East Asian summer in recent decades, against a background of global warming. This cooling trend is re-examined using station data from 1951 to 2007, and atmospheric general circulation model (AGCM) simulations are performed to investigate the possible influence of changes in external forcing. The numerical experiments are designed to investigate the effects of four types of external forcing: greenhouse gases (GHGs), Total Solar Irradiance (TSI), ozone, and the direct effects of aerosols. Results indicate that external forcing contributes to the cooling trend over East Asia. Furthermore, GHGs, and to a lesser degree the direct effects of aerosols, are the main contributors to the cooling trend. The possible linkages between the external forcings and the cooling trend are discussed.”

3 Responses to “New research from last week 40/2012”

Thanks so much for the work you do on this blog, you’re a regular part of my weekly reading and I appreciate the effort you put in. It’s rather late but I’ve finally got round to putting you on my blog roll.